Everyone should use a condom when having sex with new or casual partners

Dr Valerie Delpech

HIV cases rose after the introduction of antiretrovirals that are effective in treating the illness.

And from 1990 to 2010 there was a 26% increase in gay men having unprotected sex, according to a study at University College London.

But the findings also suggest the increase in infection would have been two-thirds higher without the new drugs.

Dr Valerie Delpech, head of HIV surveillance at the Health Protection Agency, said: “Everyone should use a condom when having sex with new or casual partners, until all partners have had a sexual health screen.”